Using Circular Polarizing Filter (a C-PL Filter)

Photographers shooting landscapes in broad daylight or shooting objects with shiny metallic surfaces or may be shooting at places with a lot of reflective material around, have something common to counter for – glare. Glares from window glass, shop displays, automobiles lined up in a car show etc. are all potential nightmares to shoot. If you have your blinkies (highlight indicators) turned on, you are likely to be warned that you are passed the red line with your highlights. While there are some photographers, who don’t quite appreciate the concept of cutting down glares and reflections, for most these are quite offending. For the latter group of photographers, circular polarizers are the only way to cut down glare.

What are C-PLs?

A circular polarizing filter (also known as C-PL), as the name tend to suggest, is like a sunglass for your camera. It does the exact same thing that your polarizing sunglasses does. It cuts down glare and blinding reflections whilst increasing color saturation. With a C-PL in front of your lens, however, you can do more than just cut down glare. A sunny sky can be hazy, light is scattered due to the particles suspended in the air, pulling contrasts down and making things appear grey. A C-PL filter will polarize the oncoming light, meaning, it will only allow light from a certain angle to pass through while filtering everything else. This has the effect of increased saturation. With a C-PL filter blue sky appears bluer, haze is eliminated and reflections are cut down. With a C-PL filter you can shoot straight down water and it will magically become transparent.

How to use a circular polarizing filter

New C-PL users often get frustrated because they are unsure as to how to get the maximum benefit out of their C-PL filters. Sometimes, as they claim, C-PLs don’t work at all and at other times the impact is dramatic almost to the extent that it looks unreal. The fact that the results can be very difficult to work out by amateurs is reason why they tend to avoid the C-PL. However, there is a very simple method of correctly using a C-PL and getting the maximum impact out of it.

Before beginning to shoot pictures point your right index finger towards the sun with your thumb pointing straight up. Now rotate the thumb whilst keeping the index finger still pointing at the sun. The C-PL will have its maximum effect along the imaginary round line that the thumb makes. Here are a before and after result of the same scene shot without and with a C-PL.

There are however some very fine adjustments to be made to be able to get proper results with a C-PL. Let’s say you are shooting a landscape scene on a clear blue day and the sun is about 2/3rds to the horizon. Now the angle of the sun to the area where you want polarization to happen will determine how much polarization will take place. As discussed above it is at the areas which are perpendicular to where the sun is which gets maximum polarization. As you move away from that area, farther towards the sun or away from it, polarization gets reduced. However, this can be tweaked as detailed in the next point.

Types of polarizing filters

There are two different types of polarizing filters. Linear and circular. If you have a digital SLR camera and are looking for polarizing filters, you should always opt for circular polarizers. Vice versa if you have a film SLR, a linear polarizer will suffice. Linear polarizers will throw modern digital SLR camera metering off and as such are not recommended.

As regards to their shapes, polarizers can either be round or square. Round polarizers are easily tweaked and they can be turned to optimize the effect of polarization. In the previous paragraph we were discussing that the angle of the sun to where you want polarization to happen will have an impact. You can also regulate the amount of polarization by turning the filter. In photographic parlance it is also known as ‘dialing-in’.

Finer tips

A circular polarizing filter will only work when it is a sunny day or at the most there are only a few patches of cloud cover. It will not work if it is an overcast day. You might as well keep it in your bag on such f/4 type overcast conditions. The best way to check the degree of polarization that you are getting is by looking through the viewfinder or at the rear LCD monitor. If the amount of polarization that you are looking at through the viewfinder is very high (almost unreal) you could dial it down. Dialing it down is a term that implies rotating the filter, reducing the angle and with it the extent of polarization. Careful composition and framing is necessary to ensure that the image does not look weird.